The two tools i learned how to use in photoshop were the Clone stamp, how to erase a face and relpace it with a different one using layers.

This is is the original version of the great balloon race picture I used the clone stamp on.  Using the clone stamp is very simple, unless you are using it when the background has two different textures.  The clone stamp copies part of a picture and replaces in over another part to give the effect you "removed it" from the photo.  Thats why when using the clone stamp if the background has two different textures it can make the edit look cheesy 

This is the edited version of the Great balloon race, as you can see all the balloons are gone, but we used the clone stamp to cover them.  The clone stamp is very helpful if you want to remove something from a picture and make it look like it was never there

This is the original picture of the hippie i used to remove a face.  I opened this in photoshop then i opened a picture of me in photoshop and copied my face and inserted it as a layer over the hippie, I then lined up my face with his by turning the opacity down on my picture so i could see through it a little bit and lined the faces up.  I then put the background layer over my face layer and began to erase the hippies face.  Mine started to come out because it was a different layer behind the first one.  I cleaned it up blurred the edges and it was done

This is the edited version version of the hippie with my face replace it.